The present invention relates to a judgement circuit for use in an adaptive filter, such as an adaptive luminance signal/chrominance signal separation filter, particularly one for separating a luminance signal and a chrominance signal from a composite television signal of the NTSC system. The judgment circuit may also be incorporated in a digital detail extraction filter that extracts details directly from an NTSC video signal with frequency-multiplexed luminance and chrominance signals.
In a prior art luminance signal/chrominance signal separation filter, the characteristics of the vertical direction filter and the horizontal filter are fixed and combined. Moreover, an assumption has been made that the picture elements forming a series of samples of the television signal which are adjacent to each other are analogous to each other. With such an arrangement, in the region where there is a sharp change in the luminance and chrominance of the picture, the luminance signal component and the chrominance signal component of each channel (line) intrude into the adjacent channel (line), causing cross coloring and dot interference thereby to deteriorate the quality of the reproduced picture.
Prior art detail extraction filters use only components of the luminance signal. This requires separate 1H delay circuit: one to delay the signal by one horizontal scan period in the luminance/chrominance separation circuit that separates the video signal into a luminance signal and chrominance signal, and another for the horizontal and vertical detail extraction filter.